(1) Field of the Invention
The present invention relates to an electric junction box, which is mounted on a motor vehicle as a mobile unit and includes draining means for draining water which ?? entered the interior of the box.
(2) Description of the Related Art
In general, a motor vehicle as a mobile unit mounts various electronic instruments, for example, lamps such as a head lamp and tail lamp, motors such as a starter motor and air conditioner motor and so on. In order to supply electric power to such electronic instruments, the motor vehicle mounts junction blocks at suitable positions. The junction block is constructed by collecting various electric circuit units such as fuses, relays and so on.
The junction block may be called a fuse block, relay box or electric junction box as a general term because the junction block may include fuses, relays, busbars and so on. In this specification, such a fuse block, relay box or junction block is called an electric junction box as a general term.
For example, an electric junction box includes: a wiring board on which electric components are mounted; a connector block having a body part and terminals, which terminals penetrate through a bottom wall of the body part and one end part of each of which terminals is electrically connected to the wiring board; and a case which is arranged above the bottom wall of the body part and which has holes each of which allows an opposite end part of the terminal to pass therethrough so as to expose the terminal, and which receives the wiring board and the connector block therein.
For example, a fuse is attached to the terminal exposed from the hole. Because the fuse can be mounted or removed from the outside of the case, maintenance work can be easily carried out. However, on the other hand, water might enter the case through the hole when maintenance work is performed, resulting in the situation such that water might adhere on the wiring board received in the case and on the electric components mounted on the wiring board, possibly causing the electric junction box to be damaged as a result of a short circuit or corrosion of the wiring board.
In order to solve the above problems, the following electric junction box has been proposed (for example, see Japanese Patent Application laid-Open No. 2003-348732). Such an electric junction box has a body part of a connector block, which includes a groove formed on an inner surface (bottom surface) of a bottom wall and a drain outlet continuing to an end of the groove. Further, a case has a tube-shaped duct extending in an upward and downward direction of the case. The duct is arranged in the case, wherein an upper opening of the duct is arranged below and spaced from an end of the drain outlet while a lower opening of the duct is opened toward the lower side of the case.
Water which enters into the case through the hole reaches the bottom surface of the connector block, is absorbed in the groove, and is drained to the outside of the connector block from the drain outlet. Thereafter, the water falls into the duct from the drain outlet, passes through the duct, and is drained to the outside of the case.
In the electric junction box disclosed in Japanese Patent Application laid-Open No. 2003-348732, the drain outlet and the upper opening of the duct are arranged to be spaced apart from each other and the drained water falls into the duct from the drain outlet. Accordingly, when the electric junction box is actually mounted on a motor vehicle, depending on vibration and vehicle angle during traveling, the water from the drain outlet might fall outside the duct or the water might collide against an inner surface of the duct so that the water scatters outside the duct. Then, such water might adhere on the wiring board or on the electric components mounted on the wiring board, causing the electric junction box to be damaged due to a short circuit or corrosion of the wiring board. Moreover, the duct provided in the case brings about a problem that a structure of the electric junction box becomes complicated and a size of the electric junction box becomes large.